Process for the preparation of anthraquinone

ABSTRACT

A simple process for preparing anthraquinone in good yield from anthracene is described, which process comprises oxidising anthracene in the liquid phase by means of oxygen or an oxygencontaining gas, in an inert organic solvent, and in the presence of cupric bromide.

United States Patent Janin et a1.

[ PROCESS FOR THE PREPARATION OF ANTHRAQUINONE I {75] Inventors; Raymond Janin, lrigny; Leon Krumenacker. Serezin du Rhone, both of France [73] Assignee: Rhone-Poulenc S.A., Paris, France [22] Filed: May 8, 1974 [21] Appl. No.: 468,139

[30] Foreign Application Priority Data May 11.1973 France 7117155 [52] U.S. Cl. 260/385; 252/441; 252/442 [51] Int. Cl. C07C 49/68; C09B 1/06 [58] Field of Search 1. 260/385 [56] References Cited UNITED STATES PATENTS 1.787.416 l2/l930 Wohl 1. 260/385 [451 Nov. 11, 1975 1.787.417 l2/l930 WOhl .1 260/385 1.880.322 10/1932 .laeger 260/385 2.h43.269 6/1953 Augustine 260/385 X 2.8247881 2/1958 Wetlslein 260/385 OTHER PUBLICATIONS Crocker et al.. J. Chem. Soc." l970(c) pp.

Prinmr E.\wuinerPau1 F Shaver Attorney. Agent, or Firm-Cushman, Darby & Cushman [57] ABSTRACT A simple process for preparing anthraquinone in good yield from anthracene is described. which process comprises oxidising anthracene in the liquid phase by means of oxygen or an oxygen-containing gas. in an inert organic solvent, and in the presence of cupric bromide 12 Claims, No Drawings PROCESS FOR THE PREPARATION OF ANTHRAQUINONE The present invention relates to a process for the preparation of anthraquinone by oxidation of anthracene by means of oxygen or an oxygen-containing gas.

Anthraquinone is a compound of great industrial value, particularly in the manufacture of dyestuffs. Various processes for the preparation of anthraquinone have been proposed, especially from phthalic anhydride (condensation with benzene in the presence of anhydrous aluminium chloride to form benzoylbenzoic acid which is converted to anthraquinone with sulphuric acid). It has also been proposed to oxidise anthracene to anthraquinone in the liquid phase by means of an oxidising agent such as nitric acid or a dichromate, or in the vapour phase by means of oxygen or air in the presence of a catalyst such as vanadium pentoxide. These various processes are not completely satisfactory either because of the reagents employed or because of the reaction conditions; it is clearly important to have available a simple process for the oxidation of anthracene in the liquid phase by means of oxygen or an oxygen-containing gas. During an investigation into the halogenation of aromatic compounds, especially phenols and amines, by means of cupric chloride in the presence of oxygen and hydrochloric acid in l,5-dimethoxy-3-oxa-pentane (diglyme), H.P. CROCKER and R. WALSER (J. Chem. Soc., 1970, I982 1986) mentioned the formation of anthraquinone from anthracene, but it was found that, under these conditions, the halogenation reaction leads predominantly to the formation of 9-chloroanthracene which deprives such a process of any value as an industrial method for the preparation of anthraquinone.

According to the present invention, there is provided a process for the preparation of anthraquinone by oxidation of anthracene in the liquid phase by means of oxygen or an oxygen-containing gas in the presence of an inert organic diluent and in the presence of cupric bromide.

It has been found, surprisingly, that the replacement of cupric chloride by cupric bromide makes it possible to alter the course of the reaction so that anthraquinone is the preponderant product and, in some cases, depending on the solvent used, so that anthraquinone is practically the only product, the formation of 9- bromoanthracene being very slight and non existant.

The diluents which are particularly suitable are linear or branched saturated aliphatic alcohols containing 1 to 10 carbon atoms, and compounds of the general formula:

in which R and R which may be identical or different, denote a hydrogen atom or a linear or branched alkyl radical containing 1 to carbon atoms, R denotes a linear or branched alkylene radical containing l to car bon atoms and n is an integer from up to 3.

More specifically, R and R can be, for example, a methyl, ethyl or propyl radical and R can be, for exam ple, an ethylene, propylene, tetramethylene, pentamethylene, hexamethylene or octamethylene radical.

Specific examples of diluents which may be used include methanol, ethanol, propanol, isopropanol, lbutanol, isoamyl alcohol, tertiary amyl alcohol, n-pentanol, l-hexanol, the octanols, ethylene glycol, 2- methoxyethanol, 1,2-dimethoxy-ethane, propane-l ,2- diol, propane-l,3-diol, 3-methoxyl-propanol, 1,3- dimethoxy-propane, 2-methyl-propane-l,3diol, 2,2- dimethyl-propanel ,3-diol, butane-1,4-diol, butane- 2,3-diol, pentane-l,5--diol, hexane-1,6-diol, diethylene glycol, dipropylene glycol, tripropylene glycol and 1,5- dimethoxy-3-oxa-pentane. Amongst these the non-condensed glycols are preferred. In fact, it has been found that the combination of cupric bromide and an aliphatic glycol, especially ethylene glycol, makes it possible to obtain excellent yields of anthraquinone.

It is, of course, possible to use a mixture of 2 or more organic diluents; it is also possible for the reaction mixture to contain water.

It has also been found, and this forms a further feature of the process of the present invention, that it is advantageous to carry out the process in the presence of one or more compounds referred to hereafter as activators, namely inorganic acids, with the exception of hydrochloric acid, iron halides (chlorides, bromides, fluorides and iodides), aluminium halides and halides of elements from Groups 3A, 4A and 5A of the Periodic Table as given in Handbook of Chemistry and Physics, 45th edition, 1964, Physics", page B-2. In fact, the presence of these compounds results in an increase in the reaction rate. Acids which have a pK in aqueous solution of less than 2, and preferably of at most 1, are the inorganic acids which may be used, for example sulphuric acid, perchloric acid, pyrophosphoric acid and hydrobromic acid. Hydrobromic acid is particularly suitable, both because of its effect on the reaction rate and because of the fact that an anion which is already present in the medium is used.

Amongst the halides used as activators, there may be mentioned ferrous and ferric chlorides, ferrous and ferric bromides, aluminium chloride, aluminium bromide, aluminium fluoride, boron trifluoride, antimony pentachloride, antimony trichloride, antimony tribromide, antimony trifluoride and pentafluoride, antimony pentaiodide, arsenic tribromide, arsenic trichloride, arsenic pentafluoride, arsenic trifluoride, arsenic triiodide and pentaiodide, and bismuth tetrachloride and trichloride. Amongst these various halogenated derivatives, those of antimony generally produce the most pronounced effect on the kinetics of the oxidation reaction, so that they form a preferred class of activators.

Although it is preferable, for reasons of convenience, to employ cupric bromide directly, it is possible to form it in situ from cuprous bromide.

The quantity of cupric bromide, expressed in mols per mol of anthracene, can vary within wide limits. Thus, for example, it can be at least l A 10 and can be as much as 2 mols per mol of anthracene. The latter value can be exceeded but, in general, it is not necessary to exceed l mol of cupric bromide per mol of anthracene.

The quantity of activator, which may be present, can also vary within wide limits, depending on the nature of the compound employed. In general terms, it can be at least 1 10 mol and can be as much as 10 mols per mol of anthracene; however, in the case of antimony halides, it is generally not necessary to exceed l mol per mol of anthracene.

The temperature at which the reaction is carried out suitably varises from 20 to 200C. A temperature of from 20 to C is generally very suitable. The oxidation is suitably carried out under a partial pressure of 3 oxygen of 0. l to 20 bars. When the diluent or the activator such as boron trifluoride, arsenic trifluoride or arsenic pentafluoride, is gaseous at the chosen temperature, it is preferable to work under pressure.

EXAMPLES 2 TO 12 Using the procedure described in Example 1, a series of tests was carried out under the conditions which are In addition to oxygen, it is possible to use mixtures of given in the following Table, as are the results obtained. oxygen with inert gases, such as nitrogen, as the oxidis- EX. Anlhru- CuBr Co-cutalyst Solvent Dura- T. in Degree Anthru- 9-bromocene in in g Weight tion in C of conquinone anthracene g Nature or volume Nature Volume hours version Yield in yield in in 7r Z k 2 7. l 2 1,4 HBr 2 cm of Ethyl- I16 cm" 7 82 24 74 0 66% strength one by weight glycol 3 4.42 8 32.5 84.5 10.3 4 1.4 cm of 38.3 87.5 8.6

66% strength by weight 5 4.42 55.5 95 4.5 6 L4 2 cm" of 100 49.5 89.5 6

66% strength by weight 7 Pro a: v 1.9 31.5 traces pane .2- diol 8 diglyme 75.2 74 25.8 9 sin, 0.40 g ethyl- I40 77 97.5 0

ene glycol l0 AlCl; 0.2 g ethyl ene glycol 120 23 99 U FeCL, 0.25 g 55 99 0 1: H 50. 5 cm" of 110 14.8 98 0 95% strength by weight By way of comparison, 7.12 g of anthracene, 6.8 g of cupric chloride dihydrate, 4 cm of fuming hydrochloing gas. Typically, air, optionally enriched with oxygen, ric acid and 116cm of diglyme were introduced into can be used. the apparatus described in Example 1. The contents of The process according to the present invention is the flask are heated at 80C for 8 hours and then cooled particularly simple to effect on a technical scale and to 20C, and the reaction mixture is treated as in Examcan be carried out continuously. pie 1. Anthracene (15.2% by weight of the anthracene The following Examples further illustrate the present introduced), 9-chloro-anthracene representing 38.6% invention. of the anthracene introduced and anthraquinone representing 36% of the anthracene introduced are mea- EXAMPLE 1 sured in the precipitate obtained.

120 cm of ethylene glycol, 7.12 g of anthracene (4 A The degree of conversion of anthracene is thus 10 mol) and 1.4 g of cupric bromide (6.2 /1 10 84.8% and the yields of 9-chloro-anthracene and anmol) are introduced into a 250 cm flask equipped with thraquinone are, respectively, 44.5% and 42.5%.

a reflux condenser, a thermometer, a dip tube for introducing gas, a stirring systen and a thermoregulated EXAMPLE 13 heating device; then the contents of the flask are 120 cm of ethylene glycol, 7.12 gof anthracene and heated to 140C with stirring. A stream of oxygen is 1.4 g of cupric bromide are introduced into a 250 cm then introduced into the reaction medium at a rate of 6 autoclave made of stainless steel lined with tantalum, to 8 l/hour under normal conditions of pressure and and then the apparatus is closed, 22 bars of air are intemperature. These conditions are maintained for 8 troduced and the temperature is raised to 140C. These hours and then the contents of the flask are cooled to conditions are maintained for 5 hours, the apparatus is 20C and poured into a sufiicient amount of water to cooled and then the pressure is released. The reaction bring the total volume to 1 liter; this causes the dismixture is treated as in Example 1. 8.53 g of a product solved anthracene to precipitate. The mixture is left to are isolated, in which anthracene (18.4% of the quanstand at ambient temperature for 12 hours and is then tity introduced) and anthraquinone representing 61% filtered through sintered glass. The precipitate obof the anthracene introduced are measured.

tained is dried to constant weight over P 0 In this The degree of conversion of anthracene is 81.6% and way, 8.02 g of a product are isolated, in which 4 g of anthe yield of anthraquinone is 75% relative to the conthracene (56% of the anthracene introduced) and 3.28 verted anthracene. No bromo-anthracene was detected g of anthraquinone (corresponding to 41.5% of the anin the products formed.

thracene introduced) are measured by chromatography on alumina. The degree of conversion is 44% and 65 EXAMPLE 14 the yield of anthraquinone relative to the anthracene converted is 94.5%, No 9-bromo-anthracene formed during the oxidation.

The procedure of the preceding Example is followed, but 0.2 cm of SbCl is introduced in addition; after reacting for l hour 35 minutes, 8.30 g of a product containing anthracene, 7% of the quantity introduced, and anthraquinone corresponding to 92.5% of the hydrocarbon introduced, are isolated.

EXAMPLE 16 The experiment of Example 2 is repeated, and then. at the end of the reaction, the filtrate is recovered and is introduced into the apparatus described in Example I, 0.4 cm of hydrobromic acid and 7.12 g of anthracene are added and the whole is heated at 82C for 8 hours. After treatment as in Example l, 7.32 g of a product containing 81.5% of the anthracene introduced and anthraquinone corresponding to 17% of the hydrocarbon introduced (corresponding to a yield of 92% relative to the converted anthracene) are recovered.

EXAMPLE 17 The procedure of Example 1 is followed, with the following compounds and under the following conditions.

CuBr 4.46 g anthracene 7.l2 g ethylene glycol 88 cm water 22 cm"' temperature l 00C duration 8 hrs.

rated aliphatic alcohol or a compound of the general formula:

in which R and R which may be identical or different. denote a hydrogen atom or a linear or branched alkyl radical containing up to 5 carbon atoms, R denotes a linear or branched alkylene radical containing up to ID carbon atoms, and n is an integer from 1 to 3.

2. Process according to claim 1, which is carried out in the presence of at least one activator which is selected from hydrobromic or sulphuric, acid an iron halide, aluminium halide, boron trifluoride, an antimony halide, an arsenic halide and a bismuth halide.

3. Process according to claim 2, in which the activator is hydrobromic acid or sulphuric acid.

4. Process according to claim 2, in which the activator is an iron chloride, aluminium chloride or antimony pentachloride.

5. Process according to claim 1 in which the inert organic solvent is a compound of the general formula (I).

6. Process according to claim 1, in which the solvent is ethylene glycol, propanediol or l,5-dim ethy0xy-3- oxa-pentane.

7. Process according to claim 1 in which the reaction is carried out at a temperature from 20 to 200C with a partial pressure of oxygen from 0.1 to 20 bars.

8. Process according to claim 1, in which the cupric bromide is present in an amount of at least I A l0 mol per mol of anthracene.

9. Process according to claim 2, in which the activator is present in an amount of at least 1 A 10 mol per mol of anthracene.

10. Process according to claim 1, in which anthracene is oxidised in the presence of cupric bromide and hydrobromic acid or an antimony halide in ethylene glycol.

11. Process according to claim 5 in which n is l.

12. Process according to claim 5 in which R, and R denote a hydrogen atom. 

1. IN A PROCESS FOR THE PREPARATION OF ANTHARAQUIONE WHICH COMPRISES OXIDISING ANTHRANCENE IN THE LIQUID PHASE BY MEANS OF OXYGEN OR AN OXYGEN-CONTAINING GAS, IN AN INERT ORGANIC SOLVENT AND IN THE PRESENCE OF A CUPRIC SALT, THE IMPROVEMENT WHEREIN THE CUPRIC SALTS IS BROMIDE AND THE INERT ORGANIC SOLVENT IS A SATURATED ALCOHOL OR A COMPOUND OF THE GENERAL FORMULA: R1-O-(R''-O)N-R2 IN WHICH R1 AND R2, WHICH MAY BE IDENTICAL OR DIFFERENT, DENOTE A HYDROGEN ATOM OR A LINER OR BRANCHED ALKYL RADICAL CONTAINING UP TO 5 CARBBON ATOMS, RH DENOTES A LINER OR BRANCHED ALKYLENE RADICAL CONTAINING UP TO 10 CARBON ATOMS, AD N IS AN INTEGER FROM 1 TO
 3. 2. Process according to claim 1, which is carried out in the presence of at least one activator which is selected from hydrobromic or sulphuric, acid an iron halide, aluminium halide, boron trifluoride, an antimony halide, an arsenic halide and a bismuth halide.
 3. Process according to claim 2, in which the activator is hydrobromic acid or sulphuric acid.
 4. Process according to claim 2, in which the activator is an iron chloride, aluminium chloride or antimony pentachloride.
 5. Process according to claim 1 in which the inert organic solvent is a compound of the general formula (I).
 6. Process according to claim 1, in which the solvent is ethylene glycol, propanediol or 1,5-dimethyoxy-3-oxa-pentane.
 7. Process according to claim 1 in which the reaction is carried out at a temperature from 20* to 200*C with a partial pressure of oxygen from 0.1 to 20 bars.
 8. Process according to claim 1, in which the cupric bromide is present in an amount of at least 1 X 10 5 mol per mol of anthracene.
 9. Process according to claim 2, in which the activator is present in an amount of at least 1 X 10 5 mol per mol of anthracene.
 10. Process according to claim 1, in which anthracene is oxidised in the presence of cupric bromide and hydrobromic acid or an antimony halide in ethylene glycol.
 11. Process according to claim 5 in which n is
 1. 12. Process according to claim 5 in which R1 and R2 denote a hydrogen atom. 